Improve remote integration-cli tests

Progress toward being able to run integration-cli campaign using a
client hitting a remote host.

Most of these fixes imply flagging tests that assume they are running on
the same host than the Daemon. Also fixes the `contrib/httpserver` image
that couldn't run because of a dynamically linked Go binary inside the
busybox image.

Signed-off-by: Arnaud Porterie <arnaud.porterie@docker.com>

integration-cli/docker_cli_attach_unix_test.go

@@ -16,6 +16,7 @@ import (
 
 // #9860 Make sure attach ends when container ends (with no errors)
 func (s *DockerSuite) TestAttachClosedOnContainerStop(c *check.C) {
+	testRequires(c, SameHostDaemon)
 
 	out, _ := dockerCmd(c, "run", "-dti", "busybox", "/bin/sh", "-c", `trap 'exit 0' SIGTERM; while true; do sleep 1; done`)